Innovative Instrumentation for the Study of Atmospheric Aerosol Optical Properties

Aerosol optical properties (i.e. scattering and absorption) are of great importance to assess aerosol effects e.g. on visibility and Earth radiation balance. In this paper, we present innovative optical instrumentation developed at the Department of Physics “Aldo Pontremoli” of the University of Milan: a multi-wavelength polar photometer (PP_UniMI) and a Single Particle Extinction and Scattering (SPES). PP_UniMI is a filter-based device providing the aerosol absorption coefficient of aerosol at 4 wavelengths (λ). Such measurements are of interest to have insights into the λ-dependent behavior of aerosol absorption properties, which is still poorly understood especially for what concerns weakly absorbing aerosol components. SPES allows to determine the size and refractive index of single particles. In case of absorbing particles, also information on the imaginary part of the refractive index—very important especially in the field of global models—can be provided with little assumptions. We describe the main features of the two instruments and their advantages and limitations. Examples of application are also presented.